When an add-on part is to be subsequently attached to an existing structure, a hole is often drilled and a fastening element is anchored in this hole. The hole is normally created using a drill. In this process, loose material (drillings and drilling dust) remains in the hole drilled in construction materials such as concrete, natural stone or solid brick, whereby the amount of material depends on the size of the drilled hole as well as on the drilling angle (e.g. vertically downwards, horizontal or vertically upwards), and this takes up about 5% to 25% of the drilled hole volume in the case of holes that are drilled vertically downwards or horizontal.
The drillings and the drilling dust have to be removed before the fastening element can be inserted so that a secure and permanent connection can be established. Especially in the case of chemical fastening systems, but also with mechanical anchors, the load-bearing capacity and durability of the fastening depends to a crucial extent on how thoroughly the drilled hole was cleaned.
Nowadays, drilled holes are generally cleaned in that drillings and the drilling dust are removed from the drilled hole by means of blowing or vacuuming devices. Subsequently, the drilling dust that had been pressed against the wall of the drilled hole during the drilling procedure is mechanically loosened by means of brushes. Finally, this loosened drilling dust then has to be removed from the drilled hole again by the blowing or vacuuming device.
The cleaning of drilled holes is an essential part of the installation procedure of fastening elements, and this pertains to the time spent, to the required tools and equipment, as well as to the quality of the fastening work. Thus, for purposes of the vacuuming procedure, aside from a suitable vacuum cleaner, there is also a need for suction tubes that are adapted to the diameter and depth of the drilled holes, since the drilled dust has to be vacuumed from the bottom of the drilled hole. When the drilled hole is blown out, especially in the case of fairly large drilled holes, pressed air is needed in order to achieve effective cleaning. Moreover, the blown-out drilling dust causes considerable dust pollution and is thus a health concern for the workers doing the job.
German patent application DE 39 19 095 A1 discloses a drilling tool, especially a stone drill, that is supposed to allow the drilling dust to already be removed at the time when the hole is being drilled, in that a helical shank of the drilling tool has brush elements that are arranged in the groove bed of a conventional drilling tool or that themselves form spiral conveying helixes. The outer diameter of the helical shank of a conventional drilling tool, however, is much smaller than the inner diameter of the drilled hole being formed, so that the drillings and drilling dust can trickle radially between the helical shank and the wall of the drilled hole, down to the bottom of the drilled hole. Although the radially protruding brush elements provided make it possible to clean adhering drilling dust off the wall of the drilled hole, they do not completely remove the drilling dust that has been loosened and that has accumulated at the bottom of the drilled hole, since the loose material can fall through the brush down towards the bottom of the drilled hole, especially if the brush rubs against the wall of the drilled hole when the drilling tool makes a rotating motion.